Many modern structures, especially large buildings, contain interior space that is substantially sealed from the external environment. The air within the interior building space must be conditioned as to temperature and humidity, and usually a minimum amount of oxygen must be supplied to occupants of the building. Fresh, outdoor air may be used to regulate the temperature and humidity within and to supply oxygen to the interior space. For example, if the outdoor air temperature generally is lower than the desired temperature within the building, then the outdoor air may be used to cool the interior space when the temperature within the interior space rises above a desired temperature, or a so-called xe2x80x9cset pointxe2x80x9d.
The air temperature may rise within a building due to several sources, such as heat from cooking utensils and light bulbs, sunlight impinging upon floors and walls, radiant heat from exterior walls and windows, and heat generated from building occupants. The amount of heat being generated in the interior space is sometimes referred to as the load of the space.
Air within the interior space of the building should be circulated in order to prevent air from becoming stagnant, which might otherwise allow pockets of extreme temperature difference to develop within the interior space and which might otherwise cause pockets of oxygen-depleted air to develop within the interior space.
It is also usually desirable to maintain the air pressure within the interior space at the same pressure as the outdoor air pressure. Consequently, as fresh, outdoor air is admitted into the interior space, air should usually be discharged in an equal quantity from the interior space into the outdoor environment.
Often, the simple admittance of fresh, outdoor air will be sufficient to maintain the temperature of the interior building space at the set point. However, many times the temperature of the outdoor air, the magnitude of the space load, and the quantity of outdoor air being admitted into the interior space is insufficient to maintain the set point, and the temperature may rise above the set point. In such situations, it is desirable to provide a heat exchanger, much like the cooling coils of a household refrigerator, over which the fresh air, as well as the recirculated interior air, passes before being introduced into the interior space. One or more heat exchangers may be utilized, with the cooling power being increased by the running of additional heat exchangers.
Conventionally, when the temperature of the interior space equals or exceeds a certain number of degrees above set point, the air conditioner is commanded to admit as much outdoor air as possible and to pass all of the outdoor air and the recirculated air past a running heat exchanger, whereby the air being supplied to the interior space is cooled. Under such command, the air being supplied to the interior space may be exceptionally cold and cause discomfort to occupants in the vicinity of air supply ducts. Also under such command, thermostats located near the air supply ducts may falsely suggest that the overall interior of the air space is lower than in reality, and thermostats located remote from air supply ducts may experience a delay in sensing a temperature reduction of the overall interior air space. A remotely located thermostat, such as a thermostat located in the return air duct that supplies air to be recirculated over the heat exchanger, may indicate that the air is at set point while the overall air temperature in the interior space may be significantly below the set point. In either event, when the thermostats sense that set point has been achieved, then they command the heat exchanger to shut down.
Since the cooling fluid in each heat exchanger must be pumped by a compressor, the starting and the stopping of the compressors that pump the cooling fluid through the heat exchangers causes compressor wear and fatigue. With conventional command systems, the compressors are started and stopped relatively frequently, which adversely effects compressor life and increases maintenance and repair costs.
The present invention relates to a system and method of regulating an air conditioner so that it helps ensure that the interior air is cooled to set point, without overcooling, and lessens the frequency with which the compressors are started and stopped, thereby enhancing compressor life and reducing maintenance and repair costs.
The present invention relates to a method and system for staging the cooling effect of an air conditioning unit in which outside air is substantially prevented from passing through the cooling unit for a prescribed time after the cooling function has been initiated.